Question: When was Nnamdi Azikiwe the President of Nigeria?
Paraphrase: What was the time period during which Nnamdi Azikiwe was the President of Nigeria?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q181782 p:P39 ?s . ?s ps:P39 wd:Q500282 . ?s pq:P582 ?value}